New challenges for the pressure evolution of the glass temperature

The ways of portrayal of the pressure evolution of the glass temperature (Tg) beyond the dominated Simon-Glatzel-like pattern are discussed. This includes the possible common description of Tg(P) dependences in systems described by dtg/dP>0 and dTg/dP<0. The latter is associated with the maximum of Tg(P) curve hidden in the negative pressures domain. The issue of volume and density changes along the vitrification curve is also noted. Finally, the universal pattern of vitrification associated with the crossover from the low density (isotropic stretching) to the high density (isotropic compression) systems is proposed. Hypothetically, it may obey any glass former, from molecular liquids to colloids

Pretransitional Behavior and Dynamics in Liquid Crystal–Based Nanocolloids

The impact of nanoparticles on phase transitions in liquid crystal (LC)—nanoparticle nanocollids is still little known. This contribution results for dodecylcyanobiphenyl (12CB), pentylcyanobiphenyl (5CB), and hexyl isothiocyanatobiphenyl (6BT) as the LC host with the addition of BaTiO3 barium titanate barium titanate nanoparticles. The latter has a strong impact on the value of dielectric constant, relaxation time, and the discontinuity of the isotropic–mesophase transitions. The first-ever high-pressure studies in such systems are also presented

Broadband dielectric studies in linseed oil: Supercriticality and the New Insight into Melting/Freezing Discontinuous Transition

The long-range supercritical changes of dielectric constant, resembling ones observed in the isotropic phase of rod-like liquid crystalline compounds, are evidenced on approaching liquid-solid discontinuous phase transition. The 'supercriticality' can be an additional factor for supporting the unique pro-health properties of linseed oil. It can also be significant for numerous technological applications. The report also reveals properties significant for melting/freezing discontinuous phase transition cognitive puzzle. Broadband dielectric spectroscopy studies revealed long-range premelting (heating from the solid phase) and post-freezing (cooling from the liquid phase) effects with critical-like parametrizations. They can be correlated with the 'grain model' for premelting and its development by the Lipovsky model. The evidence for the post-freezing effect, with the critical-like portrayal, may indicate a specific granular solidification associated with pretransitional fluctuations. Numerous hallmarks of liquid-liquid and solid-solid phase transitions have also been found. Notably, the melting temperature surrounding is related to the minimum and the freezing temperature to the maximum of dielectric loss factor D=tan(delta). Regarding dynamics, three primary relaxation processes have been found. Their changes in subsequent temperature intervals, related to the apparent activation enthalpy, follow critical-like patterns with the same singular temperature. For relaxation times evolution, it leads to optimal parameterizations via the 'critical and activated' equation, recently proposed.Comment: 14 Figures , 15 equation

Relationship between dielectric properties and critical behavior of the electric birefringence in binary liquid mixtures

We present experimental results on the critical exponent ψEKE describing the divergence of the Kerr constant of binary liquid mixtures near the critical consolute point. We show that the measured value of ψEKE agrees with the theoretical prediction only if the measurement is performed with a mixture of two liquids presenting a small mismatch in the dielectric constant, and that the measured ψEKE grows as the dielectric constant mismatch increases. Such findings are consistent with a recent model which assumes that the elongation of critical fluctations along the direction of the electric field can become so strong that fluctuations in the direction perpendicular to the electric field may cross over from Ising to mean-field behavior

Continuous Isotropic-Nematic transition in compressed rod-like based nanocolloid

Landau - de Gennes mean field model predicts the discontinuous transition for the Isotropic - Nematic transition, associated with uniaxial and quadrupolar order parameter in three dimensions. This report shows pressure-related dielectric studies for rod-like nematogenic pentylcyanobiphenyl (5CB) and its nanocolloids with BaTiO3 nanoparticles. The scan of dielectric constant revealed the continuous I-N transition in a compressed nanocolloid with a tiny amount of nanoparticles (x=0.1%). For the nematic phase in 5CB and its x=1% nanocolloid the enormous values of dielectric constant and the bending-type long-range pretransitional behavior were detected. The 'shaping' influence of pretransitional fluctuations was also detected for the ionic-related contribution to dielectric permittivity in the isotropic phase. For the high-frequency relaxation domain, this impact was tested for the primary relaxation time and the translational-orientaional decoupling.Comment: 28 pages, 7 figure

Pressure-driven relaxation processes in nanocomposite ionic glass LiFe0.75_{0.75}V0.10_{0.10}PO4_{4}

This paper presents results for systems formed in a solid glassy state after nanocrystallization process above the glass temperature. We analyze electric conductivity and relaxation processes after such treatment under high temperature (HT) and high pressure (HP-HT) as well. The latter leads to ca. 8% increase of density, two decades (100) increase of electric conductivity as well as qualitative changes in relaxation processes. The previtreous-type changes of the relaxation time on cooling is analyzed by the use of critical-like and the 'critical-activated' description. Presented results correspond well with obtained for this material and shown in ref. [8]. The evidence for pressure evolution of the glass and crystallization temperatures, indicating the unique possibility of maxima and crossovers is also reported